As a pulley apparatus such as a guide pulley or tension pulley that is assembled and used in a belt power train mechanism, pulley apparatuses having a synthetic resin pulley fastened to the outer ring of a rolling bearing made of a metal material such as bearing steel have been conventionally used in order to reduce weight and cost. FIG. 9 illustrates a construction of a pulley apparatus in which a synthetic resin pulley as disclosed in JP 10-122339 (A) is assembled. This pulley apparatus 1 is composed of a pulley 2 made of synthetic resin and around which a belt is placed, and a rolling bearing 3, which is a single-row deep-groove radial ball bearing for supporting the pulley 2 so as to be able to freely rotate around a support shaft or the like. The rolling bearing 3 comprises: an inner ring 5 having a single-row inner ring raceway 4 formed around the outer circumferential surface thereof; an outer ring 7 having a single-row outer ring raceway 6 formed around the inner circumferential surface thereof; and a plurality of rolling elements that are located between the inner ring raceway 4 and the outer ring raceway 6 so as to be able to roll freely. Moreover, a seal plate 9 is provided between the outer circumferential surface of both end section of the inner ring 5 and the inner circumferential surface of both end sections of the outer ring 7, and together with preventing grease that is filled in the internal space where the rolling elements 8 are located from leaking to the outside, prevents dust and the like from the outside getting into the internal space. The pulley 2 is fastened around the outer circumferential surface of the outer ring 7 of the rolling bearing 3 made in this way.
The pulley 2 has an inner-diameter side cylindrical section 10 and an outer-diameter cylindrical section 11 that are concentric with each other. The outer circumferential surface in the middle section of the inner-diameter side cylindrical section 10 and the inner circumferential surface in the middle section of the outer-diameter cylindrical section 11 are connected by a circular ring shaped connecting section 12, and a plurality of reinforcement ribs 13 are provided on each of both sides of the connecting section 12 in a radial shape. This kind of pulley 2 is such that the inner-diameter cylindrical section 10 is provided and fastened around the outer ring 7 of the rolling bearing 3 by injection molding. In other words, the pulley apparatus 1 is obtained by injecting molten thermoplastic resin inside a cavity having an inner shape that corresponds to the outer shape of the pulley 2 which is formed in a die with the portion near the outer circumference of the outer ring 7 molded on the inner circumference side thereof, and after this thermoplastic resin has cooled and solidified, opening the die and taking the pulley 2 with the rolling bearing 3 from the cavity.
The pulley apparatus 1 that is constructed in this way is used as a guide pulley or tension pulley which is assembled in belt power train mechanism that drives an auxiliary machine of an automobile. In other words, the inner ring 5 of the rolling bearing 3 is fitted and fastened onto a support shaft that is fastened to a stationary portion of the engine such as the cylinder block. A continuous belt is placed around the outer circumferential surface of the pulley 2. As this continuous belt moves, the pulley 2 rotates, and the contact angle and tension of the continuous belt is maintained.
In the case of a pulley apparatus 1 in which a synthetic resin pulley 2 is fastened to the outer circumferential surface of the outer ring 7, the outer ring 7 is made using metal plate such as bearing steel, so the coefficient of linear expansion of the outer ring 7 and the pulley 2 are different. Therefore, as the temperature rises during use, the adhesion between the outer ring 7 and the pulley 2 decreases, and there is a possibility that relative slipping (creep) will occur between the outer ring 7 and the pulley 2. Technology for preventing this kind of creep is disclosed in JP 61-38218 (A), JP 50-20043 (U), JP 50-23540 (U), and JP 11-148550 (A). In the pulley apparatus disclosed in JP 61-38218 (A), as illustrated in FIGS. 10A, 10B, knurling (serration) 14 is formed around the entire outer circumferential surface of the outer ring 7a, and when a synthetic resin pulley is fitted around the outside of the outer ring 7a, the knurling 14 bites into the inner circumferential surface of the pulley, which prevents creep.
Moreover, in the pulley apparatus disclosed in JP 50-20043 (U), as illustrated in FIGS. 11A, 11B, a concave groove 15a (15b) having differing width along the axial direction is formed in the circumferential direction in the outer circumferential surface of the outer ring 7b (7c), and a synthetic resin pulley is fastened to the outer circumferential surface of the outer ring 7b (7c) by injection molding. When performing injection molding, molten thermoplastic synthetic resin is filled into the concave groove 15a (15b). The concave groove 15a has differing width in the axial direction in the circumferential direction, so the inside surface of the concave groove 15a (15b) engages with the synthetic resin that is solidified inside the concave groove 15a (15b), which prevent the occurrence of creep between the outer ring 7b (7c) and the pulley.
Furthermore, in the pulley apparatus disclosed in JP 50-23540 (U), as illustrated in FIG. 12, a pair of concave grooves 15c are formed around the entire outer circumferential surface of the outer ring 7d so as to be inclined with respect to the axial direction and not parallel with each other, and a synthetic resin pulley is fastened on the outer circumferential surface of the outer ring 7d by injection molding. The pair of concave grooves 15c is inclined in the axial direction, so the occurrence of creep between the outer ring 7d and the pulley is prevented. In this construction, by making direction of inclination of the pair of concave grooves 15c opposite from each other, the axial loads that occur as the pulley rotates cancel each other out, and thus a moment load that causes pulley apparatus to twist does not occur in the outer ring 7d. 
In the construction disclosed in JP 61-38218 (A), JP 50-20043 (U) and JP 50-23540 (U), it is possible to prevent the occurrence of creep between the pulley and the outer ring 7a to 7d, however, there is still some unsolved problems. In other words, in the case of the construction disclosed in JP 61-38218 (A), knurling 14 is formed around the entire outer circumferential surface of the outer ring 7a, so when performing heat treatment after the knurling 14 is formed, there is a possibility that the outer ring 7a may deform due to residual strain. Moreover, when forming an outer ring raceway 6 around the inner circumferential surface of the outer ring 7a, it is difficult to hold the outer circumferential surface of the outer ring 7a with good precision. Therefore, there is a possibility that the workability and processing precision of the outer ring raceway 6 will decrease.
On the other hand, in the case of the construction disclosed in JP 50-20043 (U) and JP 50-23540 (U), a cylindrical surface remains on the outer circumferential surface of the outer ring 7b to 7d, so there is no decrease in the workability or processing precision of the outer ring raceway 6. However, as the performance of automobiles has increased in recent years, there is a tendency for the tension in the belt placed around the pulley and the rotational speed of the pulley to increase, and so there is increase in the force that causes creep to occur between the pulley and the outer ring. In the case where the force that causes creep is large, in the construction disclosed in JP 50-20043 (U), it is necessary to make the difference in the width dimension in the axial direction of the concave groove 15a (15b) large, and in the construction disclosed in JP 50-23540 (U), it is necessary to make the inclination angle of the concave grooves 15c large. When the difference in the width dimension of the concave groove 15a (15b) or the inclination angle of the concave grooves 15c is large, the processing area on the outer circumferential surface of the outer ring 7b to 7d becomes large.
Furthermore, in the case of the construction disclosed in JP 50-20043 (U) and JP 50-23540 (U), the shape in the width direction of the cylindrical surface that remains on the outer circumferential surface of the outer ring 7b to 7d changes in the circumferential direction. Therefore, when performing heat treatment of the outer ring 7b to 7d after the concave grooves 15a to 15c have been formed, there is a possibility that the outer ring 7b to 7d will deform due to residual strain.
FIG. 13 and FIG. 14 illustrate construction that is disclosed in JP 11-148550 (A). In this construction, a locking groove 16 is formed in part in the axial direction of the outer circumferential surface of the outer ring 7e of the rolling bearing 3a, and a straight pattern knurling 19 is formed by arranging concave sections 17 and convex section 18 alternately around the entire circumference of the bottom surface of the locking groove 16 using knurling process. Part of the synthetic resin of the pulley 2a is allowed to enter into the concave sections 17 that are formed in the bottom surface of the locking groove 16 of the outer ring 7e to form protrusions 20 that are long in the axial direction on the inner circumferential surface of the pulley 2a. The engagement between these protrusions 20 and the knurling 19 on the outer ring 7e prevents the occurrence of creep between the pulley 2a and the outer ring 7e. 
In the case of the construction disclosed in JP 11-148550 (A), the shape in the width direction of the cylindrical surface remaining on the outer circumferential surface of the outer ring 7e is the same in the circumferential direction, so even when performing heat treatment after the knurling 19 has been formed on the outer circumferential surface of the outer ring 7e, deformation of the outer ring 7e due to residual strain is prevented. However, in this construction the number, shape and dimensions of the concave sections 17 and convex sections 18 of the knurling 19 are not particularly regulated. Therefore, when the length in the circumferential direction of the bottom surface of the concave sections 17 is too short, or when the depth in the radial direction of the concave sections 17 is too deep, the part of the synthetic resin of the pulley 2a does not enter into all of the concave sections 17, so there is a possibility that gaps (voids) will occur between the inner circumferential surface of the pulley 2a and the outer circumferential surface of the outer ring 7e. Particularly, when the length in the circumferential direction of the concave sections 17 is short (essentially 0), and the cross-sectional shape of the protrusions 20 is triangular, it becomes easy of gaps to occur between the inner circumferential surface of the pulley 2a and the outer circumferential surface of the outer ring 7e. As a result, there is a possibility of looseness between the pulley 2a and the outer ring 7e, or a possibility that it will not be possible to sufficiently maintain the connecting strength between the pulley 2a and the outer ring 7e. 